JP2011223855A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device that attains both high controllability and low noise, and detects a phase current from a current of a DC power supply line.SOLUTION: The inverter device includes an inverter circuit, a current detector which detects a current between the DC power source and the inverter circuit, and a control circuit which makes the inverter circuit output an AC current to a motor by feeding electricity for PWM modulation, and corrects the electricity feeding to detect a phase current by the current detector. The control circuit detects a phase current of two or more phases in every carrier cycle when a speed command value of the motor is equal to or larger than a predetermined speed and when the speed command value of the motor is smaller than the predetermined speed and necessary torque is equal to or larger than predetermined torque, and detects a phase current of two phases in two carrier cycles when the speed command value of the motor is smaller than the predetermined speed and the necessary torque is smaller than the predetermined torque.

Description

  The present invention relates to a method for detecting a phase current from a current of a DC power supply line of an inverter device that performs PWM modulation.

  Conventionally, as this type of phase current detection method, a method of detecting from a current of a DC power supply line is known. This circuit will be described below. FIG. 6 shows an electric circuit diagram. The control circuit 12 of the inverter device 23 controls the switching element 2 via the connection line 18 based on a rotation speed command signal (not shown) and the like, and converts the electric power of the battery 1 into direct current alternating current. Thereby, an alternating current is supplied to the stator winding 4 of the motor 11 and the magnet rotor 5 is driven. The diode 3 serves as a circulation route for the current flowing through the stator winding 4.

  The detected current value of the current detector 6 is sent to the control circuit 12 and used for determination of power consumption calculation, switching element 2 protection, and the like, and further used for position detection of the magnet rotor 5. In order to detect the position, it is necessary to detect a phase current of two phases or more. However, in a specific phase and at a low output, it may not be possible to detect two phases or more within one carrier cycle. A measure for solving the problem is shown (for example, see Patent Document 1).

  As a result, two or more phases can be detected. However, since the energization period is adjusted, a ripple current is generated and noise noise is generated. As this correspondence, for example, two phases are detected in two carrier periods (see Patent Document 2). That is, by reducing the adjustment of the energization period, the ripple current is reduced and noise noise is reduced.

  Moreover, it is known also about the position detection method by calculating an induced voltage (for example, refer patent document 3). That is, the induced voltage is a voltage induced in the stator winding 4 by the rotation of the magnet rotor 5 and can be used for detecting the position of the magnet rotor 5. It is also known to relate to details of control such as the speed command value and current command value of the inverter device (see, for example, Patent Document 4).

Japanese Patent No. 4311045 (page 15, FIG. 16, FIG. 17) Japanese Patent No. 4239643 (page 14, FIG. 16, FIG. 17) Japanese Patent No. 4311045 (page 13, FIG. 2) Japanese Patent No. 4211110 (Claim 1, FIG. 1)

  In the conventional example described above, when detecting phase currents for two or more phases within one carrier cycle, the position can be detected for each carrier cycle, but the controllability is good, but noise noise is generated. On the other hand, when two phases are detected in two carrier periods, noise noise is small, but controllability is reduced. Therefore, it is necessary to use them according to the situation.

  The present invention solves such a conventional problem, and an object of the present invention is to provide an inverter device that detects a phase current from a current of a DC power supply line that can achieve both high controllability and low noise.

  In order to solve the above problems, an inverter device according to the present invention includes an inverter circuit including an upper arm switching element connected to the plus side of a DC power source and a lower arm switching element connected to the minus side, a DC power source and an inverter. A current detector for detecting a current between the circuits, and a control circuit for causing the inverter circuit to output an alternating current to the motor by energization of PWM modulation, correcting the energization and detecting a phase current by the current detector, When the motor speed command value is equal to or higher than the predetermined speed, the control circuit determines that the phase current of two phases or more per carrier cycle when the motor speed command value is smaller than the predetermined speed and the required torque is equal to or higher than the predetermined torque. When the motor speed command value is smaller than the predetermined speed and the required torque is smaller than the predetermined torque, two phases are generated in two carrier cycles. And it detects a phase current of.

  As a result, when the motor rotation speed is high (the speed command value is equal to or higher than the predetermined speed), the ratio of the carrier cycle to the motor rotation cycle is large. High controllability can be ensured by detecting the position every time. When the motor rotation number is high, the mechanical noise is large, so the influence of noise noise caused by the ripple current is small.

  Further, when the motor rotation speed is low (the speed command value is smaller than the predetermined speed), the ratio of the carrier period to the motor rotation period is small, so the phase current for two phases is detected in two carrier periods, and two carriers are detected. High controllability can also be secured by detecting the position for each cycle. Since only the phase current for one phase is detected in one carrier cycle, noise noise caused by the ripple current can be reduced.

  Furthermore, even when the motor rotation speed is low (the speed command value is smaller than the predetermined speed), if the required torque of the motor is equal to or greater than the predetermined torque, the phase current for two phases or more is detected for each carrier cycle. To do. When the motor rotation speed is low and the required torque of the motor is large, the rotation of the motor tends to become unstable. Therefore, high controllability can be ensured by detecting phase currents for two or more phases for each carrier period and detecting the position for each carrier period. When the motor rotation speed is low and the required torque of the motor is large, the energization detection possible period is increased, and thus the adjustment value of the energization period is decreased. Therefore, the influence of noise noise caused by the ripple current is reduced.

  Therefore, in the inverter device that detects the phase current from the current of the DC power supply line, it is possible to achieve both high controllability and low noise by properly using the phase current detection according to the situation.

  The inverter device of the present invention can achieve both high controllability and low noise when detecting the phase current from the current of the DC power supply line.

Electrical circuit diagram of inverter device according to Embodiment 1 of the present invention The flowchart which concerns on Embodiment 1 of this invention Functional block diagram of the inverter device Sectional drawing of the inverter apparatus integrated electric compressor which concerns on Embodiment 4 of this invention. Schematic diagram of a vehicle equipped with an inverter device according to Embodiment 5 of the present invention Electric circuit diagram of conventional inverter device

According to a first aspect of the present invention, there is provided an inverter device including an upper arm switching element connected to a positive side of a DC power source and a lower arm switching element connected to a negative side, and detecting a current between the DC power source and the inverter circuit. And a control circuit that outputs an alternating current to the motor by energizing the PWM modulation to the inverter circuit and corrects the energization and detects the phase current by the current detector. When the speed command value is equal to or higher than the predetermined speed, when the speed command value of the motor is smaller than the predetermined speed and the required torque is equal to or higher than the predetermined torque, a phase current of two phases or more is detected for each carrier cycle, When the speed command value is smaller than the predetermined speed and the required torque is smaller than the predetermined torque, the phase current for two phases is detected in two carrier cycles. It is.

  As a result, when the motor rotation speed is high (the speed command value is equal to or higher than the predetermined speed), the ratio of the carrier cycle to the motor rotation cycle is large. High controllability can be ensured by detecting the position every time. When the motor rotation number is high, the mechanical noise is large, so the influence of noise noise caused by the ripple current is small.

  Further, when the motor rotation speed is low (the speed command value is smaller than the predetermined speed), the ratio of the carrier period to the motor rotation period is small, so the phase current for two phases is detected in two carrier periods, and two carriers are detected. High controllability can also be secured by detecting the position for each cycle. Since only the phase current for one phase is detected in one carrier cycle, noise noise caused by the ripple current can be reduced.

  Furthermore, even when the motor rotation speed is low (the speed command value is smaller than the predetermined speed), if the required torque of the motor is equal to or greater than the predetermined torque, the phase current for two phases or more is detected for each carrier cycle. To do. When the motor rotation speed is low and the required torque of the motor is large, the rotation of the motor tends to become unstable. Therefore, high controllability can be ensured by detecting phase currents for two or more phases for each carrier period and detecting the position for each carrier period. When the motor speed is low and the required torque of the motor is large, the noise of the noise due to the ripple current is small because the mechanical noise is large.

  Therefore, in the inverter device that detects the phase current from the current of the DC power supply line, it is possible to achieve both high controllability and low noise by properly using the phase current detection according to the situation.

  According to a second invention, in the inverter device of the first invention, when the required torque is equal to or greater than the predetermined torque, the current command value is equal to or greater than the predetermined current value, and when the required torque is smaller than the predetermined torque, the current command value Are respectively replaced when they are smaller than a predetermined current value. Since the torque and the current value are in a proportional relationship, they can be replaced. Thereby, the current command value as the control parameter can be used as it is. Therefore, the configuration of the control software becomes easy.

  According to a third invention, in the inverter device of the first or second invention, a phase current for two phases is detected in two carrier cycles, and a carrier cycle in which no phase current is detected is provided. Thereby, noise abnormal noise resulting from the ripple current generated by detecting the phase current can be further reduced. When the motor rotation speed is low (the speed command value is smaller than the predetermined speed), the ratio of the carrier cycle to the motor rotation cycle is small, so high controllability can be secured even if a carrier cycle that does not detect phase current is provided. .

  According to a fourth aspect of the invention, in the inverter device of the first or second aspect of the invention, even when detecting the phase current for two phases in two carrier cycles, the phase current for two phases or more is generated for each carrier cycle at the time of startup. A period for detection is provided. As a result, it is possible to ensure high controllability during start-up when the rotation of the motor is likely to become unstable, and to start it reliably, and to limit the period for detecting phase currents of two phases or more for each carrier cycle. Therefore, noise noise caused by ripple current can be suppressed.

A fifth invention drives the motor of the electric compressor in the inverter device of the first to fourth inventions. Thereby, the continuous noise from the air conditioner which operates for a long time can be reduced.

  A sixth invention is an inverter device according to the first to fifth inventions, which is mounted on a vehicle. In a vehicle, since the mounting space is limited, downsizing is required, and vibration resistance against vibration due to traveling is also required, this inverter device that detects current with a single current detector such as a shunt resistor is useful. In addition, this inverter device is useful for vehicles, particularly electric vehicles and hybrid cars, because they have high quietness such as running by a motor and require low noise and low vibration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment.

(Embodiment 1)
FIG. 1 shows an inverter device 20 according to Embodiment 1 of the present invention and an electric circuit around it. The control circuit 7 of the inverter device 20 detects the phase current based on the voltage from the current detector 6 provided on the power supply line. Although the phase currents for three phases may be detected, if the phase currents for two phases are detected, the phase currents of the remaining phases can be calculated from the two current values (in the stator winding 4). In terms of nature, Kirchhoff's law of current is applied).

  Based on the current values for these three phases, the control circuit 7 calculates the induced voltage of the stator winding 4 by the magnet rotor 5 constituting the sensorless DC brushless motor 11 (hereinafter referred to as the motor 11), and the magnet rotor. 5 position detection is performed. Based on a rotational speed command signal (not shown) or the like, the switching element 2 constituting the inverter circuit unit 10 is controlled, and the DC voltage from the battery 1 is switched by PWM modulation, so that a sinusoidal AC current is generated. Output to the stator winding 4 of the motor 11. The diode 3 constituting the inverter circuit unit 10 serves as a circulation route for the current flowing through the stator winding 4. For the switching element 2, upper arm switching elements are defined as U, V, W, and lower arm switching elements are defined as X, Y, Z, and diodes corresponding to the switching elements U, V, W, X, Y, Z Is defined as 3U, 3V, 3W, 3X, 3Y, 3Z.

  The current detector 6 may be any current detector that can detect an instantaneous peak current, such as a current detector using a Hall element or a shunt resistor. Further, it may be provided on the positive side of the power supply line. If it is a shunt resistor, it is easy to realize miniaturization and improvement of vibration resistance. The control circuit 7 is connected to the upper arm switching elements U, V, W and the lower arm switching elements X, Y, Z by a connection line 18 via a drive circuit or the like, and controls each switching element. When the switching element 2 is an IGBT or a power MOSFET, the gate voltage is controlled. When the switching element 2 is a power transistor, the base current is controlled.

  FIG. 2 is a flowchart according to Embodiment 1 of the present invention. Hereinafter, in step 10 for explaining the operation, it is determined whether or not the speed command value is a predetermined value (predetermined speed) or more. If it is equal to or greater than a predetermined value (predetermined speed) (Y), step 40 detects phase currents for two or more phases for each carrier cycle. The energization period necessary for this is adjusted. Thereby, position detection is performed for each carrier cycle. If it is smaller than the predetermined value (predetermined speed) (N), the process proceeds to step 20. Here, it is determined whether or not the current command value is equal to or greater than a predetermined value (predetermined current value). If it is equal to or greater than a predetermined value (predetermined current value) (Y), in step 40, phase currents for two phases or more are detected for each carrier cycle. The energization period necessary for this is adjusted. Thereby, position detection is performed for each carrier cycle. If it is smaller than a predetermined value (predetermined current value) (N), in step 30, phase currents for two phases are detected in two carrier periods. The energization period necessary for this is adjusted. Thereby, position detection is performed every two carrier periods.

  For example, the predetermined speed is 4000 rpm, the carrier frequency is 10 kHz, and the predetermined current value is 19A. When the speed command value (number of rotations) is 6000 rpm and the current command value is 18 A, in step 40, phase currents for two or more phases are detected for each carrier cycle, and position detection is performed for each carrier cycle. When the speed command value (number of rotations) is 3000 rpm and the current command value is 20 A, in step 40, phase currents of two or more phases are detected for each carrier cycle, and position detection is performed for each carrier cycle. When the speed command value (number of revolutions) is 3000 rpm and the current command value is 15 A, the phase current for two phases is detected in two carrier cycles in step 30, and the position is detected every two carrier cycles. .

  When the speed command value (number of rotations) is 6000 rpm, the ratio of the carrier period to the motor rotation period is 1/100 (0.1 mS / 10 mS) because the motor rotation period is 10 mS and the carrier period is 0.1 mS. . When the speed command value (number of rotations) is 3000 rpm, the ratio of the carrier period to the motor rotation period is 1/200 (0.1 mS / 20 mS) because the motor rotation period is 20 mS and the carrier period is 0.1 mS. It becomes. That is, the ratio of the carrier cycle to the motor rotation cycle is ½ when the speed command value (number of rotations) is 3000 rpm compared to 6000 rpm. Therefore, if the speed command value (rotation speed) is 6000 rpm, if phase currents for two or more phases are detected for each carrier cycle and position detection is performed for each carrier cycle, the speed command value (rotation speed) is 3000 rpm. In this case, it is sufficient to detect phase currents for two phases in two carrier periods and perform position detection every two carrier periods.

  In addition, although the example which judges whether the electric current command value is more than predetermined value (predetermined electric current value) at step 20 was shown, you may make it judge whether required torque is more than predetermined torque. Regarding the method for detecting phase currents for two or more phases for each carrier cycle, various methods such as examples described in the background art can be considered for the method for detecting phase currents for two phases with two carrier cycles. Absent. Although there is a description in the background art regarding the control details of the inverter device, it is supplemented below. From the speed command value (rotation speed command signal) and the estimated speed, the current command value for the two axes of the rotating coordinate system is calculated by PI control. From the current command value and the detected current value converted into two axes, a biaxial voltage command value is calculated by PI control. The 2-axis voltage command value is converted into three phases and output. The latter PI control response is set earlier than the former PI control response.

  FIG. 3 is a functional block diagram of inverter device 20 (control circuit 7) according to Embodiment 1 of the present invention. The speed command value ω * and the speed estimation value ω output from the position / speed estimation calculation unit 85 are input to the speed control calculation unit 87. Then, proportional / integral (PI) control is performed on the difference between the speed command value ω * and the estimated speed value ω, and a current command value i * is output. Next, the two-phase current command value output unit 86 converts the current command value i * into a biaxial current command value id *, iq * and outputs the converted value. The voltage command creation unit 83 converts the biaxial current command values id * and iq * and the phase currents iu, iv, and iw detected by the current detector 6 into the biaxial current converted by the three-phase / two-phase conversion unit 84. Based on the values id and iq, the biaxial voltage command values vd and vq are calculated. The voltage command values vd and vq are converted into three-phase voltages vu, vv and vw by the two-phase / three-phase converter 82. The three-phase voltages vu, vv, and vw are applied to the inverter circuit unit 10 via the PWM control unit 81, and the motor 11 is driven. Steps 10 to 40 in the flowchart of FIG. 2 are further added to these functions. The speed command value in the flowchart corresponds to the speed command value ω * in FIG. 3, and the current command value in the flowchart corresponds to the current command value i * in FIG.

(Embodiment 2)
In the present embodiment, when the motor speed command value is smaller than the predetermined speed and the required torque is smaller than the predetermined torque, the carrier current in which the phase current for two phases is detected in two carrier cycles and the phase current is not detected. Is provided. For example, a carrier cycle in which no phase current is detected is provided between or adjacent to two carrier cycles in which the phase current is detected.

  Thereby, noise abnormal noise resulting from the ripple current generated by detecting the phase current can be further reduced. When the motor rotation speed is low (the speed command value is smaller than the predetermined speed), the ratio of the carrier cycle to the motor rotation cycle is small, so high controllability can be secured even if a carrier cycle that does not detect phase current is provided. .

  It should be noted that various carrier cycles in which no phase current is detected may be provided once, for example, when two carrier cycles for detecting a phase current are performed ten times.

(Embodiment 3)
In the present embodiment, even when the speed command value of the motor is smaller than the predetermined speed and the required torque is smaller than the predetermined torque, a period for detecting phase currents of two phases or more is provided for each carrier cycle at the time of start-up. . For example, phase currents of two phases or more are detected for each carrier period for 0.1 second.

  This ensures reliable start-up by ensuring high controllability during start-up when motor rotation is likely to be unstable, and limits the period for detecting phase currents of two or more phases for each carrier cycle. Noise noise caused by current can be suppressed.

(Embodiment 4)
FIG. 4 is a view in which the inverter device 20 is attached in close contact with the right side of the electric compressor 40. The compression mechanism 28, the motor 11, and the like are installed in the metal casing 32. The refrigerant is sucked from the suction port 33 and compressed by the compression mechanism 28 (scroll in this example) being driven by the motor 11. The compressed refrigerant cools the motor 11 when passing through the motor 11 and is discharged from the discharge port 34.

  The inverter device 20 uses a case 30 so as to be attached to the electric compressor 40. The inverter circuit unit 10 serving as a heat source is cooled by the low-pressure refrigerant through the low-pressure pipe 38. A terminal 39 connected to the winding of the motor 11 inside the electric compressor 40 is connected to the output unit of the inverter circuit unit 10. The connection line 36 fixed to the inverter device 23 by the holding unit 35 includes a power line to the battery 1 and a signal line to an air conditioner controller (not shown) that transmits a rotation speed signal.

  In such an inverter device-integrated electric compressor, the inverter device 20 needs to be small and resistant to vibration. In addition, since the air conditioner is required to have low noise noise because of its long operation time, it is suitable as an embodiment of the present invention. Moreover, in the restart which restarts after the operation | movement of a compressor stops, since the pressure difference (differential pressure) of a high voltage | pressure side and a low voltage | pressure side is large, starting becomes unstable. This can be improved by applying the embodiment of the present invention. For example, a high pressure of 2.45 MPa (low pressure 0.4 MPa) before application becomes a high pressure of 2.65 MPa (low pressure 0.4 MPa) after application.

(Embodiment 5)
FIG. 5 shows an example in which the inverter device of the present invention is configured integrally with a compressor (Embodiment 4) and applied to an air conditioner and mounted on a vehicle. The inverter device-integrated electric compressor 61, the outdoor heat exchanger 63, and the outdoor fan 62 are mounted in the engine room in front of the vehicle 60. On the other hand, an indoor fan 65, an indoor heat exchanger 67, and an air conditioner controller 64 are disposed in the vehicle compartment. Air outside the vehicle is sucked from the air inlet 66 and the air heat-exchanged by the indoor heat exchanger 67 is blown out into the vehicle interior.

Vehicles, particularly electric vehicles and hybrid cars, are required to have a small and lightweight vehicle air conditioner from the viewpoint of ensuring running performance and mounting properties, and among them, they are heavy, and they are also heavy in a narrow motor room or engine room or other places. Reduction in size and weight of the electric compressor attached to the space is an important issue. In addition, quietness such as running by a motor is required, and low noise and low vibration are required. It is also necessary to have vibration resistance against vibration during traveling.

  The inverter device of the present invention can achieve downsizing and vibration resistance and low noise by the configuration of one current detector such as a shunt resistor described in the above embodiments. Therefore, the inverter device of the present invention is very suitable for these vehicles.

  As described above, since the inverter device according to the present invention can achieve both high controllability and low noise in detecting the phase current from the current of the DC power supply line, it can be applied to various consumer products and various industrial equipment.

DESCRIPTION OF SYMBOLS 1 Battery 2 Switching element 3 Diode 4 Stator winding 5 Magnet rotor 6 Current detector 7 Control circuit 10 Inverter circuit part 11 Sensorless DC brushless motor 20 Inverter device 40 Electric compressor 60 Vehicle

Claims (6)

An inverter circuit comprising an upper arm switching element connected to the positive side of a DC power source and a lower arm switching element connected to the negative side; a current detector for detecting a current between the DC power source and the inverter circuit; An inverter device comprising: a control circuit that causes the inverter circuit to output an alternating current to the motor by energization of PWM modulation, and that corrects the energization and detects a phase current by the current detector. When the motor speed command value is equal to or higher than the predetermined speed, or when the motor speed command value is smaller than the predetermined speed and the required torque is equal to or higher than the predetermined torque, phase currents of two phases or more are detected for each carrier cycle. When the speed command value of the motor is smaller than the predetermined speed and the required torque is smaller than the predetermined torque, two carriers Inverter device for detecting the phase currents of two phases in the period. An inverter circuit comprising an upper arm switching element connected to the positive side of a DC power source and a lower arm switching element connected to the negative side; a current detector for detecting a current between the DC power source and the inverter circuit; An inverter device comprising: a control circuit that causes the inverter circuit to output an alternating current to the motor by energization of PWM modulation, and that corrects the energization and detects a phase current by the current detector. When the motor speed command value is equal to or higher than the predetermined speed, and when the motor speed command value is smaller than the predetermined speed and the current command value is equal to or higher than the predetermined current value, a phase current equal to or greater than two phases per carrier cycle is obtained. If the motor speed command value is smaller than the predetermined speed and the current command value is smaller than the predetermined current value, two carriers are detected. Inverter device for detecting the phase currents of two phases in the period. 3. The inverter device according to claim 1, wherein when detecting phase currents for two phases in the two carrier cycles, a carrier cycle that does not detect phase currents is provided. 3. The inverter device according to claim 1, wherein even when detecting phase currents for two phases in the two carrier periods, a period for detecting phase currents for two phases or more is provided for each carrier period at startup. . The inverter apparatus of any one of Claims 1-4 which drive the motor of an electric compressor. The inverter apparatus of any one of Claims 1-5 mounted in a vehicle.